Centrifuges



CENTRIFUGES Filed Jan. 27, 1960 Fig. 2 l7 Jn ve n for WERNER SIEPE- yMLZW 191- roQnIE-YS United States Patent i 3,050,190 CENTRFFUGES WernerSiepe, Dusseldorf, Germany, assignor to Hein Lehman & Co.Aktiengesellschaft File-d Jan. 27, 1960, Ser. No. 4,906 Claims priority,application Germany Feb. 25, 1959 4 Claims. (Q. 210-380) This inventionrelates to centrifuges for the continuous separation of mixtures ofsolids and liquids. The centrifuge in accordance with the invention isintended mainly for treating sugar masses and is of the type whichcomprises a perforated centrifuge drum which is rotated about a verticalaxis and which widens from the bottom upwards, and two annular chambersarranged concentrically around the drum. The two annular chambers areseparated from one another by a partition extending to the upper edge ofthe drum. The inner of the two chambers receives the liquid which passesthrough the openings in the drum and the outer chamber receives thesolids leaving over the top edge of the drum.

In known centrifuges of the above type, it is difficult to obtain aperfect seal around the annular slot between the top edge of the drumand the partition separating the two annular chambers from one another,with the result that a portion of the liquid discharged through theperforations of the centrifuge drum may easily pass through the annularslot between the edge of the drum and the partition into the outerannular chamber which contains the solids which have been separated out,thereby making these solids wet again and making separation lesscomplete. This may happen in two ways: Firstly, the liquid which hasbeen separated out may creep up the partition and secondly the liquidmay travel in the form of a fine mist or droplets, together with the aircurrent produced by the rotation of the centrifuge drum, through theannular slot in the direction of the outer annular chamber which isintended to receive the solids. It has been found that it is the latterwhich is particularly important because the ventilation effect isparticularly great in centrifuges which rotate at high speed. Thiseffect is accentuated because the rotary parts of the centrifuge do nothave a smooth outer surface, for reasons of strength, and thestrengthening ribs or the like contribute quite considerably to theventilation effect.

Previous proposals for solving this problem mainly consist in sealingoff the annular gap between the upper edge of the drum and the partitionby making the stationary machine parts and the rotating machine partsinterengage in the form of a labyrinth. A baffle plate has been providedfor this purpose at the top edge of the rotating centrifuge drum. Thisplate widens downwardly and projects a short distance into anintermediate chamber situated between the inner and the outer annularchamber. The liquid escaping from the annular slot which is to betrapped is separated in this intermediate chamber. Really satisfactoryresults have not been obtained by this means, however, because arelatively strong air current is produced which is directed from theinner to the outer annular chamber and allows the liquid to escape inthe form of fine spray into the annular chamber for the solids.

The present invention is concerned with the problem of providing anefiective seal in centrifuges of the above mentioned type in the annulargap between the upper edge of the drum and the partition, so that escapeof liquid both as such and in the form of vapor or mist is safelyavoided.

To this end, according to the present invention, in a centrifuge of thetype described, an annularguide plate projects downwards and outwardsfrom the top edge of 3,050,190 Patented Aug. 21, 1962 the drum into theinner annular chamber and a second guide plate projects downwards intothe inner annular chamber from the partition, the guide plates formingbetween them a downwardly tapering flow chamber having an annular gap atits bottom, rotation of the drum causing an air current to passdownwards through this slot into the inner chamber.

The constant current of air produced in this way when the centrifuge isin operation prevents sprays or mists of liquid passing through theannular slot between the top edge of the drum and the partition. At thesame time, the movement of liquid as such along the partition isprevented because the downwardly projecting, preferably cone-sha-ped,guide plate attached to the partition does not allow such a movement totake place.

The above described flow of air in the flow chamber and in the annularslot at the bottom of the flow chamber may be enhanced, according to afurther feature of the invention, by surrounding the perforatedcentrifuge drum with a cone-shaped jacket with only a small distancebetween the drum and the jacket. This space becomes a suction space onrotation of the drum and has an open upper end which lies close to thetop of the guide plate which is also preferably conical and which isfixed to the edge of the drum. The advantage of constructing the drum inthis way with a cone-shaped jacket surrounding it is not only in that itincreases the flow of air and liquid along the guide plate of the drum,which in turn strengthens the air current in the flow chamber, but alsothat the suction space between the perforated drum and the conicaljacket exerts suction on the material to be centrifuged, which increasesthe separation of liquid along the perforated drum.

An embodiment of a centrifuge in accordance with the invention and itsmode of operation will be described with reference to the accompanyingdrawing in which:

FIGURE 1 is a vertical section through the centrifuge; and,

FIGURE 2 is a similar section, but to a larger scale, of a part only ofthe centrifuge.

The sugar centrifuge shown in FIGURE 1 comprises a centrifuge drum 2which is disposed in a housing 1 and is rotated about a vertical axis.The centrifuge drum 2 is conical with the base of the come at the topand is mounted on a base 5 which is supported on the bottom 4 of thehousing 1 by a rubber buffer 3. The drum 2 is driven by a shaft 6 whichpasses vertically through the base 5 and is rotated by an electric motor10 through a pulley 7, a V-belt 8, and a pulley 9. To the bottom of thecentrifuge drum 2 is fitted an accelerator cup 11 which widens upwardlyand to which the mixture to be separated is supplied centrally through apipe 12. The mixture passes from the cup 11 with increasing accelerationto a perforated separating wall 2' of the drum 2. Pipes 1 3 and 14 forthe supply of solvents, detergents and bleaching agents are provided andend in suitable discharge openings at the inner surface of the wall 2.Two annular chambers 15, 16 which are separated by a partition 17 arearranged concentrically inside the housing 1. The inner chamber 15receives the molasses passing through the openings of the wall 2 whilethe solids, in the present case sugar crystals, which pass over theupper edge 2 of the centrifuge drum 2 collect in the outer annularchamber 16. The partition 17 tapers conically in the upper portion 17'and extends to the upper edge 2" of the drum 2 with which it encloses anannular slot 18.

To prevent the liquid molasses in the annular chamber 15 from passingthrough the annular gap .18 into the chamber 16 which is reserved forthe sugar crystals, frustoconical guide plates 19 and 20 are fixed oneto the upper edge 2 of the drum and the other to the partition 17. Boththe plates 19 and 20 project downwards into the annular chamber 15. Asshown most clearly in FIG- URE 2, the two conical guide plates 19, 2t)enclose an annular fiow chamber 21, which has at its bottom an annulargap 22. As the guide plate 19 rotates at high speed with the drum 2 andwidens towards the bottom in the shape of a cone, a flow of air which isconstantly directed downwardly as indicated by the arrow 23 isestablished in the flow chamber 21 and particularly in the annular gap22 while the centrifuge is in operation. This prevents liquid vapor ordroplets from passing from the inner annular chamber through the annulargap 18 into the outer collecting chamber 16. A baffle plate 24 which isfixed to the partition '17 above the flow chamber 21 also helps toproduce this effect.

The above described aerodynamic sealing of the annular gap 18 can beimproved by surrounding the wall 2 with a conical jacket '25 which isarranged at a slight distance from the wall 2 of the drum. This conicaljacket is sealed at the bottom to the body of the drum 2. Together withthe wall 2', it forms a suction chamber 26 the upper, open end 27 ofwhich is situated near the top end of the frustoconical guide plate 19which is connected to the drum. The conical jacket 25 which is fixed tothe drum 2 and rotates with it produces a current of air and liquidwhich is deflected at the upper end of the guide plate 19, facing thewall 2', and thus reinforces the current already present on the innerside of the guide plate 19. The consequence of this is that the currentof air in the annular gap 22, which effects the actual scaling, isreinforced by an injector action. The conical jacket 25 also has a veryfavorable effect on the separating process itself, since the suctioneffect from the suction space 26 causes intensive separation of liquidthrough the perforation in the wall 2. The above described fiow effectswhich form the centrifugal process as such and also separate from eachother the two annular chambers which take up the liquid and the solidsmay, if desired, be further enhanced by providing more guide surfaces.It has been found, however, that the above described means, inparticular the conical guide surfaces 19 and and the conical jacket aregenerally sufficient because they produce by themselves a sufiicientlystrong air current.

The invention thus produces flow conditions and ventilation effects, bysuitable construction of the centrifuge drum and of the parts situatednear the annular gap 18, to obtain satisfactory sealing of the annulargap and also assists the separation process itself, so that the overalleffect of a considerably more satisfactory sepanation is obtained. Ifdesired, the above mentioned flow condi tions may be assisted orenhanced by blowing in air or similar gaseous media in the desireddirection.

I claim:

1. A centrifuge for the continuous separation of a liquid from solidsadmixed therewith, comprising a housing, a drum in said housing with anopen end and a perforated peripheral wall of generally conicalconfiguration rotatable about an upright axis, said wall divergingtoward said open end along said axis, a generally conical jacketrotatable with said drum about said axis and externally surrounding saidwall with clearance, said wall and said jacket defining between them anannular suction space with an annular outlet at an upper end of saidsuction space, a stationary partition dividing the interior of saidhousing into an inner and an outer chamber concentrically surroundingsaid drum and said jacket, and guide means on said drum diverginglyextending downwardly and outwardly from said outlet toward saidpartition and defining therewith an annular flow space terminating in anannular gap through which sealing air is drawn downwardly into saidinner chamber from said outer chamber through said flow space by therotation of said drum, said guide means including a downwardly andoutwardly directed surface terminating at said gap and disposed adjacentsaid outlet for directing a fluid mass along the latter from said outletpast said annular gap, thereby promoting the flow of said sealing air.

2. A centrifuge for the continuous separation of a liquid from solidsadmixed therewith, comprising a housing, a drum in said housing with anopen end and a perforated peripheral wall of generally conicalconfiguration rotatable about a substantially vertical axis, said walldiverging upwardly toward said open end along said axis, a generallyconical jacket rotatable with said drum about said axis and externallysurrounding said wall with clearance, said wall and said jacket definingbetween them an annular suction space with an annular outlet at an upperend of said suction space, a stationary partition dividing the interiorof said housing into an inner and an outer chamber concentricallysurrounding said drum and said jacket, first frustoconical guide meanson said drum divergingly extending downwardly and outwardly from saidoutlet and second frustoconical guide means convergingly extendingdownwardly and inwardly from said partition toward said first guidemeans and defining therewith an annular flow space terminating in anannular gap through which sealing air is drawn downwardly into saidinner chamber from said outer chamber through said flow space by therotation of said/ drum, said first guide means including a downwardlyand outwardly directed surface terminating at said gap and disposedadjacent said outlet for directing a fluid mass along the said surfacefrom said outlet past said annular gap, thereby promoting the flow ofsaid sealing air.

3. A centrifuge for the continuous separation of a liquid from solidsadmixed therewith, comprising a drum with an open end and a perforatedperipheral wall of generally conical configuration rotatable about asubstantially vertical axis, said wall diverging upwardly toward saidopen end along said axis, a generally conical jacket rotatable with saiddrum about said axis and externally surrounding said well withclearance, said wall and said jacket defining between them an annularsuction space with an annular outlet at an upper end of said suctionspace, stationary wall means forming a chamber around said drum and saidjacket, first frustoconical guide means on said drum diverginglyextending downwardly and outwardly from said outlet, secondfrustoconical guide means convergingly extending downwardly and inwardlyfrom said stationary wall means toward said first guide means anddefining therewith an annular fiow space terminating in an annular gapthrough which sealing air is drawn downwardly into said chamber fromsaid flow space by the rotation of said drum, said first guide meansincluding a downwardly and outwardly directed surface terminating atsaid gap and disposed adjacent said outlet for directing a fluid massalong said surface from said outlet past said annular gap, therebypromoting the flow of said sealing air, and baffie means extendinginwardly from said second guide means toward said first guide meansabove said annular gap.

4. A centrifuge for the continuous separation of a liquid from solidsadmixed therewith, comprising a housing, a drum in said housing with anopen end and a perforated peripheral wall of generally conicalconfiguration rotatable about a substantially vertical axis, said walldiverging upwardly toward said open end along said axis, a generallyconical jacket rotatable with said drum about said axis and externallysurrounding said wall with clearance, said wall and said jacket definingbetween them an annular suction space with an annular outlet at an upperend of said suction space, a stationary partition dividing the interiorof said housing into an inner and an outer chamber concentricallysurrounding said drum and said jacket, a first frustoconical guide meanson said drum divergingly extending downwardly and outwardly from saidoutlet, second frustoconical guide means convergingly extendingdownwardly and inwardly from said partition toward said first guidemeans and defining therewith an annular flow space terminating in anannular gap through which sealing air is drawn downwardly into saidinner chamber from said outer chamber through said flow space by therotation of said drum, said first guide means including a downwardly andoutwardly directed surface terminating at said gap and disposed adjacentsaid outlet for directing a fluid mass along said surface from saidoutlet past said an nular gap, thereby promoting the flow of saidsealing air,

6 and bafile means extending inwardly from said second guide meanstoward said first guide means above said annular gap.

References Cited in the file of this patent UNITED STATES PATENTS

